1. Field of the Invention
The present invention relates to an arteriosclerosis inspecting apparatus for inspecting arteriosclerosis of a living subject based on augmentation index.
2. Related Art Statement
Since a pulse wave that propagates in a blood vessel is reflected at a bifurcated or tapered portion of the blood vessel, a detected waveform of the pulse wave consists of an incident-wave component produced when blood is ejected from subject""s heart and propagates toward subject""s peripheral portion, and a reflected-wave component produced when an incident wave is reflected. Pulse-wave augmentation index, generally known as AI, indicates a proportion of a reflected-wave component of a pulse wave to an incident-wave component of the same. Usually, augmentation index AI is determined as a percentage of a value obtained by dividing, by a pulse pressure of a detected pulse wave, a difference obtained by subtracting, from a magnitude of the pulse wave at the time of occurrence of a reflected-wave component of the pulse wave, a magnitude of a peak point of an incident-wave component of the pulse wave.
As arteriosclerosis advances, the proportion of reflected-wave component of pulse wave increases and accordingly augmentation index increases. Thus, augmentation index is hopeful as an index used to evaluate arteriosclerosis.
As described above, augmentation index is determined based on the waveform of a pulse wave. However, the waveform of pulse wave is influenced by not only arteriosclerosis but also various parameters such as blood pressure. Thus, the augmentation index determined in the conventional method may largely vary or fluctuate and, at the present stage, it is difficult to evaluate arteriosclerosis based on the augmentation index only.
It is therefore an object of the present invention to provide an arteriosclerosis inspecting apparatus which assures that arteriosclerosis of a living subject can be diagnosed with high accuracy based on augmentation index.
The above object has been achieved by the present invention. According to a first aspect of the present invention, there is provided an apparatus for inspecting arteriosclerosis of a living subject, comprising a pulse-wave detecting device which detects a pulse wave from a portion of the subject; an augmentation-index determining means for determining, based on the pulse wave detected by the pulse-wave detecting device, an augmentation index indicating a proportion of a reflected-wave component of the pulse wave to an incident-wave component thereof, so that the arteriosclerosis of the subject is inspected based on the augmentation index determined by the augmentation-index determining means; at least one waveform-related-information obtaining device which obtains at least one sort of waveform-related information that is related to a change of a waveform of the pulse wave detected by the pulse-wave detecting device; a display device; an augmentation-index displaying means for operating the display device to display the augmentation index determined by the augmentation-index determining means; and a waveform-related-information displaying means for operating the display device to display, in addition to the augmentation index, the waveform-related information obtained by the waveform-related-information obtaining device.
According to this aspect of the present invention, the waveform-related-information obtaining device obtains the waveform-related information that is related to the change of the waveform of the pulse wave, and the waveform-related-information displaying means operates the display device to display, in addition to the augmentation index, the thus obtained waveform-related information. When a person inspects arteriosclerosis of the subject based on the augmentation index, the person can evaluate the augmentation index while taking into account the waveform-related information. Therefore, the person can diagnose, with improved accuracy, arteriosclerosis of the subject based on the augmentation index.
According to a preferred feature of the first aspect of the present invention, the arteriosclerosis inspecting apparatus comprises a plurality of waveform-related-information obtaining devices which obtain a plurality of sorts of waveform-related information, respectively, each of which is related to the change of the waveform of the pulse wave detected by the pulse-wave detecting device, and the waveform-related-information displaying means operates the display device to display, in addition to the augmentation index, the plurality of sorts of waveform-related information obtained by the plurality of waveform-related-information obtaining devices.
According to this feature, the display device simultaneously displays the augmentation index and the plurality of sorts of waveform-related information. Thus, the person can evaluate the augmentation index while taking into account the plurality of sorts of waveform-related information. Therefore, the person can inspect, with higher accuracy, arteriosclerosis of the subject based on the augmentation index.
According to another feature of the first aspect of the present invention, the waveform-related-information displaying means operates the display device to display, in addition to the augmentation index, a multidimensional graphical representation of the plurality of sorts of waveform-related information obtained by the plurality of waveform-related-information obtaining devices.
According to this feature, the person can easily observe, at a glance, the plurality of sorts of waveform-related information.
According to a second aspect of the present invention, there is provided an apparatus for inspecting arteriosclerosis of a living subject, comprising a pulse-wave detecting device which detects a pulse wave from a portion of the subject; an augmentation-index determining means for determining, based on the pulse wave detected by the pulse-wave detecting device, an augmentation index indicating a proportion of a reflected-wave component of the pulse wave to an incident-wave component thereof, at least one waveform-related-information obtaining device which obtains at least one sort of waveform-related information that is related to a change of a waveform of the pulse wave detected by the pulse-wave detecting device; and a corrected-augmentation-index determining means for correcting, based on the waveform-related information obtained by the waveform-related-information obtaining device, the augmentation index into a corrected augmentation index which is determined by the augmentation-index determining means when the waveform-related information obtained by the waveform-related-information obtaining device is equal to a pre-set standard value, so that the arteriosclerosis of the subject is inspected based on the corrected augmentation index determined by the corrected-augmentation-index determining means.
According to this aspect of the present invention, the waveform-related-information obtaining device obtains the waveform-related information that is related to the waveform of pulse wave that influences the augmentation index, and the corrected-augmentation-index determining means corrects the augmentation index into a corrected augmentation index which would be determined by the augmentation-index determining means if the waveform-related information would be equal to a pre-set standard value. Thus, the corrected augmentation index is freed of the influence of fluctuations of the waveform-related information, and accordingly a person can inspect, with improved accuracy, arteriosclerosis of the subject based on the corrected augmentation index.